This invention relates to a device and a method for inserting filters in disposable pipette tips.
In the past twenty years laboratory procedures, particularly in the medical field, have turned almost exclusively to disposable pipette tips. Further, the number of tests performed have resulted in multiple pipetters utilizing several tips at one time. As the name implies the disposable pipette tip is used once and thrown away principally for an insurance that the sample will not be contaminated by a reused pipette.
With the criticality of tests becoming more important particularly in the medical field due to the impact on the patient, the elimination of all forms of contamination has become even more critical. One area that has not been adequately addressed in the past is the possibility of contamination of the sample from the ambient gas be it air or some other gas in the pipetter as the sample is drawn into the pipette tip. In like manner, there may be particulate matter in the pipetter which could contaminate the biological sample. With a filter in the tip such a possibility is to all intents eliminated.
In addition to the possible contamination of the sample by the ambient air or gas in the pipetter, there further exists the possibility that the sample drawn into the tip will come in contact with the pipetter through carelessness in use of the instrument or through failure of the instrument itself. Should contact of the sample with the pipetter occur, it may be necessary to destroy the pipetter due to the inability of the user to properly insure decontamination of the instrument.
Accordingly, it has become incumbent upon the manufacturers of disposable pipette tips to insert a filter in the tip that will reside between the sample and the pipetter. The requirements of the filter are that it be porous to the air or gas utilized to create the suction in the pipette tip itself thereby permitting the sample to be drawn into the tip and that it be sufficiently absorbent so that should any liquid in the sample move upward in the tip, the filter will be sufficiently large to block free flow of the sample into the upper portion of the tip. Finally, the tip should be sufficiently impervious to gas and air so that there would be no immediate mixing of the gas or air that is contained in the pipetter with the sample drawn into the pipette tip before the sample is ejected into the sample dish. In like manner, if there are any aerosol contaminants in the vicinity of the sample the filter can prevent, to a great extent, such aerosols from migrating into the vicinity of the pipetter with possible contamination of the pipetter.
The description above relates to contamination of the pipetter by a sample being drawn into the pipette tip. In laboratory procedures it is equally likely that a testing fluid will be added to a biological sample by means of the pipetter to perform a test or determine the outcome of the particular test. Such testing fluids added to samples may range from a simple acid basic tests to much more complex biological tests wherein materials may be added to the sample to promote growth over a period of time in order to determine the presence or absence of bacteria or a virus or the like. In these instances it is particularly important that the reagent or the like drawn up into the pipette tip for use in application to a biological sample be contaminant free. Thus, in the manner described above, the presence of a filter can insure to a great degree the safety of the test.
While filters have been placed in pipette tips in the past, the positioning of the filter in the tip is tedious and time consuming in that it is hand labor. That is, the tips have filters inserted by individuals requiring the filter to be carefully inserted in the tip and then tamped into position one tip at a time. Such efforts have added immensely to the costs of filter equipped tips. Further, while the use of humans in such a process may insure that each tip receives a filter, it cannot insure that the filters be properly placed as each tip may receive a slightly different treatment.
Finally, as a corollary to the presence of a filter in a tip, such a filter is a good indication of the capacity of the pipette tip. That is the position of the filter in the tip can be used as an indication of an overfill if the fluid in either the sample or the reagent is drawn up to the level of the filter. Thus, a pipetter that is utilized for a half milliliter sample would have the filters positioned in the disposable tip sufficiently far up from the tip end so that a half milliliter sample or reagent may be drawn into the tip without contact with the filter. Should the operator observe the sample or reagent reaching the filtered area then it will become immediately apparent that an over supply of sample or reagent had been drawn into the pipette tip and the test can be abandoned at that point.
It is for this latter reason that the human insertion of filters and pipette tips becomes difficult as the human could position the filter at an incorrect point in the tip.
It is therefore an object of this invention to provide a device that inserts filters into pipette tips.
It is a further object of the invention to provide a machine that will cut filters from an elongated piece of filter material and insert the cut filter at a proper position in the pipette tip.
It is also an object of this invention to cut filters of sufficient length so that adequate filter protection is provided in the pipette tip.
It is still another object of this invention to provide a machine which includes a turntable in which pipette tips are positioned so that filters may be inserted therein.
It is still another object of this invention to provide means associated with the turntable wherein the positioning of the pipette tip in the turntable may be checked prior to the insertion of a filter therein.
It is also an object of this invention to provide means for position the filter at a particular point in the pipette tip.
It is another object to this invention to check to insure that the pipetter tip has had a filter properly placed therein.
Finally, it is an object of this invention to include means for withdrawing pipette tips from the turntable after the filter has been inserted.